1. Field of the Invention
The present invention relates to a vertical trench IGBT (Insulated Gate Bipolar Transistor) and a method for manufacturing the same.
2. Background Art
Conventionally, the emitter layer of a vertical trench IGBT has been formed by impurity injection and heat treatment. For miniaturizing the cell structure of a vertical trench IGBT, the contact structure must use plugs. However, a contact plug has contacted with the semiconductor layer via a thin barrier metal.
In horizontal transistors, the formation of a diffusion layer by impurity diffusion from polysilicon, or the provision of a polysilicon film between a semiconductor layer and a contact plug has been proposed (for example, refer to Japanese Patent Application Laid-Open No. 8-97226, Japanese Patent Application Laid-Open No. 9-246493, and Japanese Patent Application Laid-Open No. 9-92628).